1. Field of the Invention
The present invention relates to a method and an apparatus for controlling cooling and a method and an apparatus for detecting an abnormality in a battery pack system. The battery pack system is composed of a plurality of battery pack blocks, each of which is constituted by connecting a plurality of cells in series, that are connected with one another in series, in parallel, or by a combination of serial connection and parallel connection.
2. Description of Related Art
A conventional battery pack system, as shown in FIG. 6A, includes a battery pack block 11 that is composed of a plurality of cells connected in series; a cooling fan 2 for cooling the battery pack block 11; a temperature/voltage/current detecting section 13 for detecting the temperature, voltage, and current of the battery pack block 11 based on output signals of various sensors (not shown) mounted on the battery pack block 11; and a control section 14 for performing various control and alarm functions, including controlling operation of the cooling fan 2 according to the results of detection by the temperature/voltage/current detecting section 13. Reference numerals 15a and 15b denote output terminals of the battery pack block 11.
With reference to temperature control of the battery pack block 11, as shown in FIG. 6B, should the temperature of the battery pack block 11 rise, the tooling capacity will be raised almost proportionally by increasing the air flow rate from the cooling fan 2. This prevents a rise in the temperature of the battery pack block 11 from exceeding a predetermined temperature.
As an example of a specific configuration of the battery pack block 11, a battery pack block is known in which individual battery modules consist of a serially connected arrangement of, for example, six cells. The battery modules are disposed in parallel with 20 to 30 modules being serially connected. Thereby, an output voltage from one hundred and several tens of volts to several hundred volts can be obtained. To respond to the demand for battery pack systems with greater capacity and higher output, a battery pack system is considered which consists of an arrangement with a serial or parallel connection, or with a combination of serial and parallel connections, between a plurality of battery pack blocks as described above.
However, in such a battery pack system, the respective cooling fans 2 of a plurality of battery pack blocks are controlled by a single cooling mode of operation. Consequently, a variation in the temperatures of the battery pack blocks 11 cannot be avoided, causing a variation in the SOC (State of Charge) of the battery pack blocks 11, and further resulting in various degradation rates. Further, variations in the SOC due to partial replacement of the battery pack blocks 11, also result in differing degradation rates.
What is worse, variations in the temperature between the battery pack blocks 11 greatly promote degradation of some of the battery pack blocks 11. This has a negative effect on the other battery pack blocks 11, and results in a shortened life for the battery pack system.
In a method for detecting temperature abnormalities in each battery pack block 11, the difference between an estimated battery temperature and an obtained battery temperature is considered. The estimated value is obtained from a heat generation value calculated from charged and discharged capacities derived from current and voltage values, and the cooling capacity of the cooling fan 2. The actual temperature value is detected by a sensor. An abnormality in the battery pack block 11 is judged when the difference in the estimated and actual detected temperatures exceeds a threshold. However, this method necessitates the provision of a memory for the calculation of estimated temperature. This results in a higher cost and, in addition, tends to cause errors in the estimation value, giving rise to problems in the accuracy of the abnormality detection.